Machines for lapping and grinding



May 29, 1956 s. w. HoARE MACHINES FOR LAPPING AND GRINDING 6Sheets-Sheet 1 Filed Feb. 2. 1953 May 29, 1956 s. w. HOARE 2,747,338

MACHINES'FOR LAPPING AND GRINDING Filed Feb. 2, 1953 GSh'eet's-Sheet 2May 29, 1956 s. w. HoARE 2,747,338

MACHNES FOR LAPPING AND GRINDING Filed Feb. 2, 1955 y 6 Sheets-Sheet 3f* myn/Tol;

wz/1% w wf/- i W@ we M WM May 29, 1956 s. w. HoARE 2,747,338

MACHINES FOR LAPPING AND cmbgnmc Filed Feb. 2. 195:5 6 Sheets-sheet 4May 29, 1956 s. w. HOARE 2,747,335

MACHINES FOR LAPPING AND GRINDING Filed Feb. 2. 1953 6 Sheets-Sheet 5zA/VE/VTOR By. warm, M] M f 504,51 mvo/in/Evs May 29, 1956 s. w. HOARE2,747,338

MACHINES FOR LAPPING AND GRINDING Filed Feb. 2, 1953 6 Sheets-Sheet 6United States Patent O MACHINES Fon 'LAPPING AND oRlNmNG Stanley WilliamHoare, Peterborough, England, assiguor to The Newall Engineering'Company Limited, Peterborough, England, a BritishV company ApplicationFebruary 2, 1953, Serial No. 334,560

Claims priority, application Great Britain September 12, 1952 Thisinvention comprises improvements in or relating to machines for lappingor grinding, and is concerned with lapping or grinding machines of thetype in which the work is performed by co-operation of relativelyrotatable parts mounted, on the one hand, upon a machine base or bedand, on the other hand, upon a machine head supported over the base.

According to the present invention, in a machine of the type describedthe machine head is constituted by a bridge structure supported at both`its ends upon columns which are adapted to be rigidly anchored at theirlower ends to the machine base. The bridge structure and columns may beintegral with one another, for example in the form of a frame work ofinverted U-shape.

ln one construction, a lapping machine, according to the invention maycomprise a machine base, a bridge structure upon the base and twosupporting columns therefor one at each end of the bridge structure,which columns are adapted to be rigidly anchored at their lower ends oneto each side of the machine base, a lower lap assembly mounted on theymachine base between the columns for rotation about a vertical orsubstantially Ver tical axis and carrying above the base an abrasivewheel, and an upper lap assembly mounted on the bridge structure forrotation about the same vertical axis and carry ing below said structurea second abrasive wheel to eo-operate with the hrst mentioned wheel insimultane ously lapping both upper and lower faces of work pieces heldbetween the laps, said upper lap assembly being arranged for verticalmovement upon the bridge strncture towards and away from the lower lap.

Previously in vertical lapping machines the upper lap has been carriedupon a head supported cantilever-fashion by a single column at the rearof the machine. lt is found that with lapping machines constructedaccording to the present invention work can be inished to appreciablyliner limits than could be achieved with prior machines, presumablyowing to the fact that the bridge structure supported on two columns ismore rigid and deects less under load than a machine head carried on asingle column as a cantilever. Furthermore, ma chines embodying thebridge construction can, in general, be designed to take up less floorspace than a machine having a single column at the rear.

Further features of the invention will be apparent from the followingspecific description of a lapping machine in accordance with theinvention, given by Way of ex ample and with reference to theaccompanying drawings.

ln the drawings:

Figure l is a general perspective view of the machine,

Figure 2 is a front sectional elevation of the lower lap assembly andthe driving mechanism therefor,

Figure 3 is a front elevation, in part section, of the upper part of themachine showing the upper lap in full view,

Figure 4 is a side elevation, in section on the line 4-4 r'ice of Figure3, showing the upper lap assembly and driving mechanism therefor,

Figure 5 is a diagrammatic layout of the hydraulic circuits of themachine,`

Figure -6 is a section through a control valve of the machine, A

Figure 7 is section through a relief valve, and

Figure 8 is a plan view, in part section, of a diamond dresser unit forthe laps,

Referring firstly to Figures l and 2, the machine has a lower framemember 11 constituting the machine base which rests upon the door, andthe lower lapping member i2 is carried for rotation above the machinebase upon ay robust casting all keyed to the upper end of a hollowvertical spindle 13 mounted in said base. The spindle and the casting 40run on two robust large diameter tapered roller bearings 14, 15. Thelower lap rspindle 13 is dri-ven by a two speed electric motor (notshown) through a worm 16 and gear wheel 17 enclosed in an oil bath. Anupper frame 18 of inverted U-shape (.Figures l and 3) has the lower endsof its two limbs `or columns 19 supported upon the machine base 11 oneon Veach side of the lower lap, and a vertical sleeve 21 (Figure 4) ismounted in ball bearings 22 in a housing 39 on top of the bridge piece2li connecting the upper parts of the columns 19 of the U-shaped frame18 to rotate above the lower lap and about the same vertical axis, thesleeve 21 being driven in the opposite directional sense to the lowerlap through a worm 23 and gear wheel 24 by a single speed electric motor3S. A shaft 25 journalled in the sleeve 21 is slidable verticallytherein but is constrained to rotate therewith by means of feather keysor splines 26, and is coupled at its lower end to the spindle 27 of theupper lap 28 which spindle rotates in a quill .29 that is axiallyslidable in a vertical guide-bore 30 in the bridge piece Ztl of the U-shaped frame 18, a ball bearing 31 for the spindle 27 being provided inthe quill 29- at the upper end of the spindle. Thus, the upper lap 28which is mounted upon the lower end of its spindle 27 and runs upon aroller bearing 32 provided around an extension 33 of the lower end ofthe quill 29, is able, while being rotated, to move vertically towardsand away from the lower lap 12.

The lower and upper laps are each tted with bonded abrasive wheels 34,35 in annular form. For flat lapping, the work is normally held inposition between the two abrasive wheels by means of a work holderconsisting, for example, of a disc of wood or metal with a series ofcut-outs around the disc to receive a plurality of similar work pieces.The Work holder rests on the abrasive Wheel 34 of the lower lap l2 andthe Work pieces are laid in the cut-outs'of the Worl; holder so thattheir lower faces are in contact with the wheel. The laps are then setin rotation and the upper lap 2S is brought down until its abrasivewheel 55 presses upon the faces of the work pieces; it will be clearthat the work holding disc must be chosen of a thickness less than therequired finished thickness of the work pieces. During lapping the workpieces are caused to perform a to and fro or orbital motion with respecttothe axis of the laps by means of three eccentric pins 36 locatedwithin the annulus of the lower abrasive wheel and iitting intocorresponding holes in the work holder, which pins are driven from avertical shaft 112, passing up through the hollow spindle 13 of thelower lap, by means of adjustable planetary gearing situated within thehollow interior of the large rotary casting tu carrying the lower lap.The planetary gearing for driving the pins is not shown in the drawingssince it is a well know mechanism, not forming part of the presentinvention. The shaft 112 is coupled to the lower lap spindle 13 througha train of gear wheels 113, 114, 115, 116.

ployed for cylindrical lapping, the work holder being held, in thiscase, in the correct offset position with respect to the axis of the lapby means of a guide-bar instead of being gyrated by the eccentric pins36. Lapping iluid, such as parain, is fed to the abrasive wheels 34, 35through a exible hose 41 connected to an annular duct 42 carried by aflange 43 upon the lower end of the quill 29 which surrounds the upperlap spindle 27, from which duct the iluid runs down to the lappingsurfaces through apertures 44 in the upper lap within the annulus of theabrasive wheel 35 carried thereby and thus on to work holder. The usedfluid drains to a sump 45 in the machine base and is led away to a tanknot shown.

The weight of the upper lap 28 is sustained, and the lap is raised andlowered, by hydraulic power. Two piston and cylinder units 46 (Figure 3)with their axes vertical are mounted on the bridge piece 20 of theU-shaped of the lap axis, and have piston rods 47 extending downwardlyfrom the cylinders which rods are fastened to opposite ends of atransverse yoke L38 that is rigidly secured to, and extends laterally inboth directions from, the aforementioned iiange 43 upon the lower end"of the quill 29. Each of the piston and cylinder units 46 comprises twocylinder chambers 49, 50 arranged end to end with a piston working ineach, and the piston rod extending upwardly into the cylinders from theyoke 4S is common to both pistons and connects them to slide as one.

A hydraulic pressure is maintained beneath the piston 51 in the lowercylinder chamber 49 of each of the two piston and cylinder units 46sufficient to sustain the dead weight of the upper lap assembly, whilethe upper cylinder chambers 50 and pistons 52 therein are employed asdouble -acting units for raising and lowering the upper lap 28 and forapplying the working pressure between the laps.

j'55which also has a connection 56 to exhaust and can be operated atwill to put the upper ends 57 of the upper cylinder chambers 50 incommunication with pressure through line 59 and the lower ends 5S ofsaid cylinder 'chambers with exhaust through line 60 or vice versa, ac-

cording to whether the upper lap is to be lowered or .'raised. The upperends of the lower cylinder chambers 49 are permanently connected toexhaust through lines 94, 95 communicating with line 56 while thepressure line 61 to the lower ends of said chambers includes a pistonjvalve 62 which acts as a hydraulic lock to prevent the pressure fluidin said cylinders from escaping quickly and allowing the upper lapassembly to descend rapidly in the event of failure of the pressuresupply. The piston 63 of said piston valve 62 (see Figure 3) issubjected to the fluid pressure in the supply line 53 through a pipe 64which normally holds it in the open position against spring pressure,but if the supply pressure fails the piston is spring urged into theclosed position and communication between the supply line 53 and thelower cylinder chambers 49 is automatically cut off.

The control valve 55 (Figure 6) for the upper cylinder chambers 50 is arotary valve comprising a valve body 104 having a bore 105 in which acylindrical valve member 112 works. The valve body 104 has four portsleading into the bore and spaced at 90 intervals, one pair of oppositeports 106, 107 being connected to pressure and to exhaust respectivelywhile the other pair 108, 109 are connected to the upper ends 57 of theupper cylinder chambers 50 and to the lower ends 58 respectively. Thecylindrical member 112 in the bore 105 has arpair of channels 113 cut inopposite sides of its cylindrical surface parallel with, and symmetricalwith respect to, a diameter of said member, one of thechannels havingits ends extended somewhat by grooves 117, and the channels 113 serve toconnect one of the ports 108, 109 communicating with the upper cylinderchambers to pressure and the other to exhaust in accordance with thesetting of the valve. The four ports 106, 107, 108, 109 of the controlvalve are produced simply by drilling circular bores in the valve body104, but the pressure supply port 106 is extended on the side adjacentthe port 108 communicating with the upper ends 57 of the upper cylinderchambers 50, by a shallow channel 110 of decreasing depth cut in theinterior surface of the valve and allowing a gradual cut-olf oradmission of pressure fluid to the upper ends of said chambers 50 to beachieved whereby the speed on descent of the upper lap and the workingpressure between the laps may be regulated at will. The control valve55, which is illustrated in the closed position, thus serves both as areversing valve and also as a speed and pressure control valve. A visualgauge 111 is provided to register the pressure in the line 59 leading tothe upper ends 57 of the cylinders 50, which pressure is proportional tothe working pressure at the laps during lapping.

The pump delivering to the hydraulic system is provided with a reliefvalve 65 (Figure 7) on the delivery, which valve comprises a valve bore66 connected at one end to the pressure line 67 and at the other end toan exhaust line 68 and a piston 69 working in the bore. The piston 69 isnormally held near the pressure line end of the bore 66 by a valvespring 70 but when the pressure becomes excessive the piston is forcedback along the bore until it reaches an enlarged section 71 of the borewhich enables pressure iluid to escape past the piston 69 to exhaust. Inthis construction of relief valve, the valve piston is not sosusceptible to sticking in the bore as in the case where one or bothline connections are made through the side wall of the bore.

A micrometer dead stop device 72 (Figures 3 and 4) is mounted on thefront of the bridge piece 20 of the U- shaped frame member 18 in guides73 which allow it to be slid vertically and clamped in any desiredposition. The device comprises a substantially horizontal lever 74mounted on a horizontal pivot 75 which lever extends through a slot 82in the wall of the bridge and carries a feeler 76 which lies in the pathof a shoulder 77 on the quill 29 of the upper lap. When the feeler 76 ispushed down by the quill the opposite end of the lever 74 abuts againsta stop 78 having a micrometer adjuster 79 and also pushes up anoperating rod 80 for a visual dial indicator 81. The device may also, ifdesired, incorporate a warning lamp to light up just before dead stop isreached.

For dressing the abrasive wheels 34, 35 a diamond dresser unit S3(Figures l, 3 and 8) is rigidly mounted upon one limb 19 of the U-shapedframe member 18. The diamonds 84, two of which are normally used, onefor the upper lap and one for the lower, are adjustably mounted on heads86 on the end of a carrier bar 85 which is rigidly connected with aguide bar 87 parallel to itself and slidable in guides 88 to enable thediamonds to traverse the abrasive wheels in a radial direction. Theguide bar 87 and guides 88 are of robust construction and nished to veryline limits in order to avoid play and ensure that the wheels will betraversed as accurately as possi-ble, and the carrier bar itselfconstitutes the piston rod for a piston 90 of a double acting piston andcylinder unit 89 for operating the dresser. The piston and cylinder unit89 is supplied with pressure iluid from lthe pressure line 54 of theaforedescribed hydraulic system through a pipe 92 and a control valve 91is provided for the dresser similar in construction to the valve 55 forcontrolling the vertical movement of the upper lap, so .that the speedat which the abrasive wheels are traversed by the diamonds can beregulated and very slow speeds obtained. The exhaust line for thedresser unit is indicated at 93.

"Since the dresser unit is fixed with respect tothe axis of the upperlap 28, the upper wheel 35 is dressed first, Vand is Ithen broughtparallel to the face of the lower wheel 34 by shifting the U-s'hapedframe member 1S upon the machine base 11; then the lower wheel 34 isdressed. The lower endsof the limbs 19 of the U-shaped mem-ber 18 aresecured to the machine base 11 by means of three adjusting bolts 96 andtwo fixed bolts 97. Two of the adjusting bolts 96 are shown in Figures land 3, while the remaining adjusting bolt which is not visible in thedraw-ings is located at the back of the left-hand limb of the U-shapedmember 18, in Ka position corresponding to that occupied by the likebolt shown at the front of said limb in Figures l and 3. The two fixedbolts 97 are located one at the front of the right-hand limb, as shownin Figures l and 3, and lthe other in a corresponding position at theback of said limb. The U-shaped member 18 'is shifted on the base 1I byloosening the two fixed bolts 97, adjusting the adjust-able bolts 96 asdesired and then retightening the fixed bolts. It will be appreciatedthat provided the surfaces of `the abrasive wheels 34, 35, and theiraxes of rotation, are parallel to one another it is immaterial if thelap axes are not quite vertical; consequently, there is no need forlevelling of the machine base on the oor. A clamp operated by ahandwheel 98 is provided for immobilising the quill 29 while the upperlap is being dressed.

All the controls for the machine 1are conveniently mounted upon thefront of the U-shaped frame member 18. The motors are controlled from apress button switch panel 99 and provision is made for stepwiserotation, or inching of the lower lap, in order to facilitate loadingand unloading of the work pieces from the operators Station at the frontofthe machine and thereby obviate any disadvantage which might otherwiseresult from the fact that the limbs 19 of the U-shaped member 18 preventaccess to the laps from the sides of the machine.

A vertically movable annular splash Vguard 100 is suspended around thelaps upon chains 101 which` run over pulleys 102 on the limbs 19 of theU-shaped member 18 and carry counterbalance weights within the machinebase 11. The machine is readily portable horizontal holes 103 beingbored through therbase to receive lifting bars around which sling-s maybe placed.

I claim:

l. A lapping machine comprising in combination a machine base, anover-frame on the base said over-frame having two upst-anding limbs withtheir lower ends anchored to the base and a bridge portion supportedbetween the upper ends of the limbs, a lower lap mounted upon the baseand between the limbs of the over-frame for rotation about asubstantially vertical axis said lower lap bearing above the base asubstantially horizontal upwardly-facing lapping surface, an upper lapmounted upon the bridge portion of the over-frame above the lower lapfor both vertical movement and rotation about an axis co-linear with theaxis of the lower lap, said upper lap bearing a substantially horizontaldownwardly-'facing lapping surface to co-operate with the lappingsurface ot' the lower lap, driving means for relatively rotating theupper and lower laps, hydraulically-operated means for lowering andlifting the upper lap towards and away from the lower lap, ahydraulically-operated dresser unit mounted on one of the limbs of theover-frame for dressing the lapping surfaces, said dresser unitcomprising guide means secured to the limb of the over-frame, aguide-member slidable in said guide means and dressing heads on theguide-member to traverse the lapping surfaces as the guide-memberslides, and a piston-andwylinder `dresser-operating unit connected tothe guidemember and hydraulic connections including pressure supply andexhaust lines extending to the means for lowering and lifting the upperlap and the dresser unit.

2. A lapping machine according to claim l wherein there is provided inthe pressure supply line a relief valve comprising a valve-tbody with avalve-bore formed therein, a valve-piston working in the bore, aconnection at one end of the valve-bore to the press-ure line and aconnection at the other end of the valve-'bore to exhaust, saidvalve-bore having a portion of enlarged diameter which extends in thelongitudinal direction of the bore for a distance greater than thedistance between the opposite faces of the valve-piston, and a spring inthe valve-bore to bear upon the valve-piston and urge it toward thepressure line connection, said spring serving normally to hold the valvepiston on the pressure side of the enlargement in the valve bore butyielding when over-pressure occurs in the pressure line until the pistonarrives at said enlargement whereupon pressure flu-id is able to flowpast the piston to exhaust.

3. A lapping machine comprising -in combination a machine base, anover-frame of inverted U-shape upon the base with the lower ends of itslimbs anchored to the base and the portion connecting the limbs forminga bridge above the base, a lower lap mounted upon the base and betweenthe limbs of the over-frame for rotation about a substantially verticalaxis said lower lap bearing above the base a substantially horizontalupwardly-facing lapping surface, an upper lap mounted upon the bridgeportion of the over-frame above the lower lap for both vertical movementand rotation about an axis co-linear with the axis of the lower lap,said upper lap bearing a substantially horizontal downwardly-facinglapping surface to co-operate with the lapping surface of the lower lap,driving means for rotating the upper and lower laps in oppositedirections, hydraulically-operated means mounted on the over-frame forlowering and lifting the upper lap towards and away from the lower lap,and a hydraulically-operated dresser unit for dressing lthe lappingsurfaces mounted on one of the limbs of the over-frame said dresser unitcomprising guide means secured to the limb of the over-frame, aguide-member slidable in said guide means and dressing heads on theguide-member to traverse the lapping surfaces as the guide-memberslides, and a pistonaand-cylinder dresseroperating unit connected to theguide-member.

4. A lapping machine comprising in combination a machine base, anover-frame on the base said over-frame having two upstanding limbs withtheir lower ends anchored to the base and a bridge portion supportedbetween the upper ends of the limbs, a lower lap mounted upon the baseand between the limbs of the over-frame for rotation about asubstantially vertical axis said lower lap bearing above the base asubstantially hori- Zon-tal upwardly-facing lapping surface, an upperlap mounted above the lower lap for both vertical movement and rotationabout a substantially vertical axis and bearing a substantiallyhorizontal downwardly-facing lapping surface to co-operate with thelapping surface of Ithe lower lap, a supporting member for the upper lapwhich member is mounted on the bridge portion of the overframe so as tobe slidable vertically with the lap but is constrained against rotation,the upper lap being constrained against axial movement with respect tothe supporting member but free to rotate relatively thereto, drivingmeans for relatively rotating the upper and lower laps, and a pair ofpiston-and-cylinder units mounted on the bridge portion of theover-frame and coupled to said supporting member, and wherein eachpiston-and-cylinder unit comprises two cylinder chambers, two pistonsworking one in each chamber, and a common piston rod connecting the twopistons, and one cylinder chamber has a pressure-line connection to thespace below the piston therein through which pressure fluid is suppliedfor supporting the upper lap, while the other cylinder chamber has afirst fluid line communicating with its lower end and a second fluidline communicating with its upper end and valve means are provided forconnecting said rst iluid line to pressure and the second to exhaust,and vice versa, whereby the upper lap can be raised'and lowered at will.

v5. A lapping machine according to claim 4 wherein the valve meanscomprises a ported valve block with a valve bore therein and a rotaryvalve member working in'the bore, the valve block having four ports forconnection respectively to pressure, to exhaust and to the lluid linescommunicating with the upper and lower ends of the cylinder chamberscontrolling lifting and lowering of the upper lap and the rotary valvemember being formed with channels therein whereby appropriate pairs ofthe valve ports can be brought into communication by rotation of saidvalve member, and the pressure supply port is extended on one side by arecess of progressively decreasing cross-section formed in the wall ofthe valve bore whereby a gradual admission and cut-off of pressure uidto and from the upper ends of said cylinder chambers controlling liftingand lowering of the upper lap can be achieved.

6. A lapping machine according to claim 5 whereinautomatically-operating valve-means is provided in the pressure linesupplying pressure uid to the cylinder chambers for supporting the upperlap such that if the supply pressure fails said cylinder chambers areisolated by said valve means so that the pressure fluid in the cylinderchambers is trapped therein.

7. A lapping machine comprising in combination a machine base, anover-frame on the base said overframe having two ups'tanding limbs withtheir lower ends anchored to the base and a bridge portion supportedbetween the upper ends of the limbs, a lower lap mounted upon the baseand between the limbs of the over-frame for rotation about asubstantially vertical axis said lower lap bearing above the base asubstantially horizontal upa substantially horizontal downwardly-facinglapping sur- L face to co-operate withthe lapping surface of the lowerlap, driving means for relatively rotating the upper and lower laps,hydraulically-operated means for lowering and lifting the upper laptowards and away from the lower lap, and a hydraulically-operateddresser unit mounted on one of the limbs of the over-frame for dressingthe lapping surfaces, said dresser unit comprising guide means securedto the limb of the over-frame, a guide bar slidable in said guide meansand diamond dressing heads on the guide bar Ito traverse the lappingsurfaces as the guide bar slides, and a double-acting pistonand-cylinderunit connected to the guide bar.

8. A lapping machine comprising in combination a machine base, anover-frame on the base said over-frame having two upstanding limbs withtheir lower ends anchored to the base and a bridge portion supportedbetween the upper ends of the limbs, a lower lap mounted upon the baseand between the limbs of the over-frame for rotation about asubstantially vertical axis said lower lap bearing above the base asubstantially horizontal upwardly-facing lapping surface, a supportingmember for an upper lap which member is mounted on the bridge portion ofthe over-frame so as to be slidable vertically but is constrainedagainst rotation, an upper lap carried above the lower lap by saidsupporting member and constrained against axial movement with respectthereto but free to rotate relatively thereto about a substantiallyvertical axis, said upper lap bearing a substantially horizontaldownwardly-facing lapping surface to co-operate with the lapping surfaceof the lower lap, driving means for relatively rotating the upper andlower laps, and means connected between the bridge portion of theover-frame and the aforesaid supporting member for lowering and liftingthe upper lap towards and away from the lower lap, and wherein there isprovided a dead-stop device comprising a carrier mounted for verticaladjustment on the over-frame, a rocking lever pivoted on the carrier andarranged to extend at one end into the path of part of the supportingmember for the upper lap so that when the upper lap nears the limit ofits downward travel said supporting member engages the lever and rocksvit, an adjustable stop mounted on the carrier to limit said rocking ofthe lever and thereby arrest the downward movement of the upper lap, andmeans operatively connected with the lever for visually indicating theapproach of the lap to the dead-stop position.

References Cited in the le of this patent UNITED STATES PATENTS 240,966Chappell May 3, 1881 1,424,764 Knowles Aug. 8, 1922 1,598,341 FraserAug. 3l, 1926 1,634,745 Fraser July 5, 1927 1,843,300 Player et al Feb.2, 1932 2,085,005 Cole June 29, 1937 2,176,481 Waldron et al. Oct. 17,1939 2,209,711 Young July 30, 1940 2,374,928 Frauenthal May l, 19452,387,044 Silven Oct. 16, 1945 2,664,711 Howlett Ian. 5, 1954 2,690,034Laverdisse Sept. 28, 1954

